Electrothermally-responsive device



- Feb. 7, 1928. $1,658,254

G. R. RADLEY ELECTROTHERMALLY RESPONSIVE DEVICE Filed Aug. 16. 1920 Patented Feb. 7, 1928.

UNITED srATEs PATET OFFICE.

' GUY R. LE Y, 0F MILWAUKEE, WISCONSIN, ASSEGNOR TO THE CUTLER-HAWK MFG. (10.,0]? MILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIN.

' ELECTROTHERMALLY-RESPONSIVE DEVICE.

Applieation filed August 16; 1920. Serial No. 403,871.

This invention relates to electro-thermally responsive devices and is particularly adapted to use in association with electric circuits difl'erent electrical conditions of which are subjected to material variations.

An object of the invention is that of providing a device of the character stated, response of which is susceptible to influence in accordance with both current and voltage variations of an electric circuit.

Another object is that of providing such a device wherein provision is made for automatically varying the sensitiveness thereof to changes in one of said electrical conditions, such variation to be efiected in response to changes in the other of said electrical conditions.

Another object is that of providing such a device having inverse time element characteristics.

Other objects and advantages will hereinafter appear.

The invention will be described particularly with reference to its adaptation to isolated electric generating or so-called farm lighting systems, which systems are usually provided with an internal combustion engine to act as a prime mover and with a dynamo electric machine to be connected with a storage battery and which may be caused to act as a motor for cranking the engine.

In the control of such systems it has heretofore been proposed to provide tor starting the engine in the manner aforementioned to thereafter drive said dynamo electric machine as a generator for supplying the load circuit and also for charging the battery automatically upon the connection'of any lam or other translating device across said loa circuit. It has also been proposed to provide for interrupting the cranking circuit of the dynamo electric machine automatically in case for any reason the engine fails to start. Y

According to the present invention it is proposed to employ an electro-thermally responsive device for performing said lastmentioned function and to subject such device to influence of both the current and the ,voltage of said machine to thereby automatically vary the period of inefiective cranking permitted in accordance with different degrees of resistance to starting of the engine.

The accompanyin drawing illustrates such an adaptation 0 same will now be described, it being understood that the invention is capable of em bodiment in other forms and relations fallmg within the scope of the appended claims.

In the drawing,

Figure 1 is a schematic and diagrammatic view illustrating a particular adaptation of the invention to so-called farm lighting systems;

Fig. 2 is a side elevational view illustrating certain features of the invention more in detail;

Fig. 3 is a front elevational view of the assembly of parts illustrated in Fig. 2; while,

Fig. 4 is a plan view of the same from beneath.

Referring to Fig. 1 of the drawing, the same illustrates an electric generating plant comprising a load circuit indicated by lines L L a dynamo electric machine 5 to supply electrical energy thereto and to a storage battery 6 and an internal combustion engine 7 to act as a prime mover for driving said machine, the latter to be connected across said battery for action as a motor to crank said engine. An electro-responsive starting switch 8 is adapted to close automatically for completing the cranking circuit of said machine upon connection of any one or more translating devices across the load circuit. An electro-responsive load switch 9 is adapted to close automatically whenthe voltage of saiddynamo electric machine acting as a generator reaches a given value, thereby connecting said machine to the load circuit. Closure of said load switch serves to insure interruption of the energizing circuit of said starting switch, while a speed responsive device 10 also provides for interruption of said circuit when or soon after the engine begins firing regularl In addition to the foregoing known arrangement of instrumentalities, an electrothermally responsive device 11, is arranged to efiect interruption of the energizing circuit of said starting switch subject to an automatically regulable time element should the engine fail to develop power.

Said device 11 may advantageously comprise a pair of normally engaging contacts 12, 13, a pivoted lever 14 biased by gravity the invention and the to cause separation of said contacts and a thermally releasable latching device 15 to restrain said lever, said latch being subjected to electro-thermic influence in ac cordance with both the current and the voltage of the cranking circuit while the dynamo electric machine is acting as a motor.

In practice said latching device 15 preferably comprises a longitudinally slotted bimetallic element to be connected in series in the cranking circuit and hence to be traversed by the cranking current while a heating element 16' is arranged in thermally conductive and electrically insulated relation to said latch, the terminals of said heating element to be connected across the cranking circuit, whereby the element 15 is further subjected to electro-thermic influence in accordance with the voltage of said circuit. The sensitiveness of said device to variations in either of such electrical conditions is thus adapted to be changedautomatically in response to variations in the other of such electrical conditions. i

The device 15 is calibrated to act under the joint heating effect of its shunt and series elements for release of the lever 14 and consequent opening of the switch 8 should the engine rotate without developing power during cranking for a period, such for example as one minute. However, should the engine fail to rotate under the cranking torque of the dynamo electric machine, the initial inrush of current to said machine continues at a value several times that taken by the machine during normal running, thus tending to reduce very rapidly the battery voltage and consequently the energization of the shunt heating element 16 and should such reduction in energization of said element occur more rapidly than the development of heat thereby, said element if unassisted might be rendered incapable of efiecting releaseof the latch. Such contingency, however, is obviated by the action of the series element which, under the foregoing conditions, is strongly energized, the calibration and adjustment preferably being such that the joint heating efiect of said elements shall effect tripping of the latch following a relatively short interval of time during which the engine fails to rotate.

vFor intermediate conditions the cranking period will be automatically adjusted in accordance with the opposition offered by the value. The rate of heating of the thermally responsive device. being proportional to the sum of the squares of the current and the A. preferred construction of the thermally responsive device is illustrated in Figs. 2,

the thermally responsive device is 3, and 4 which show an insulating base 17 to which the resilient contacts 12 and 13 are rigidly. secured by means of terminal bolts 18 and 19. An angle bracket 20 is also secured to said base by means of terminal bolts 21 and 22' the lever 14 which is also of angular formation being pivotally supported adjacent the projecting end of said bracket. One extremity of said lever 14 is reflexed as illustrated and provided. with an insulated stud 23 located between the contacts 12 and 13, the relation being such as to efl'ect a gravity bias of said lever for causing said stud to engage contact 12 for moving the latter out of engagement with its co-operating contact 13. The series element 15 of likewise secured in forwardly projecting relation to thebase 17 by means of terminal bolts 24 and 25, the free end of said element being bent downwardly to engage and hold a suit able lug 26 formed integral with or rigidly secured to the lower free end of the lever 14.-

A push button 27 is also secured to such portion of said lever. The shunt element 16 cured to the element 15 by means of clips 28 but insulated therefrom.

Heating of said device to a predetermined temperature causes the same to bend upwardly for release of the lug 26 whereupon the lever 14 moves under its bias-for elfecting opening of the switch, and following cooling of the device the switch may be manually reset by means of the push but:

ton 27, while obviously closure of the switch may be efiected and maintained at any time by holding in said push button manually. The aforedescribed circuit connections for the various switch parts are efiected in an obvious manner by means of terminal bolts including'those aforedesignated.

In addition to the foregoing operative characteristics of the device the same ossesses the characteristic of inherent ad ustment to climatic temperature variations, whereby in the particular adaptation. described said device is adapted automatically to prolong the permitted period of cranking under lower. atmospheric temperatures which tend to prolong the time required to efi'ect starting ofthe engine.

Further, should the load lines become I I short-circuited at any time, the switch 9 engme whereby in no case is the drain upon the battery permitted to exceed a given tends to open, its energizing circuit being connected in shunt relation to the load circuit, thus tending to cause telegraphing of the various control switches with consequent repeated breaking of abnormally "heavy currents thereby incident to repeated starting and stopping of the engine and generator, whereby the battery may be subjected to intermittent dischargingat an abnormal rate.

7 However, under such conditions the device 15 is adapted to be heated rapidly and cumulatively during each period of closure of the switch 8, whereby following a relatively brief period of such telegfaphing said device is adapted to interrupt the energizing circuit of said switch 8 positively and permanently thus preventing further automatic starting of the .engine pending voluntary resetting of said device by means of its push button.

The device thus provides adequate protection of the various controller parts and of the battery against damage due to the foregoing causes. Also in an analogous manner the device serves to protect the battery against chargingat an abnormally high rate should either the speed responsive device 10 or the auxiliary contacts of the switch 9 or both of said instrumentalities fail to perform its or their intended functions.

What I claim as new and desire to secure by Letters Patent is:

1. Ina controller for an electric circuit subjected to current and voltage variations, the combination with a switch, of operating means therefor comprising a member tending to elt'ect operation thereof and releasable restraining means for said member comprising an electro-thermally responsive element having parts subjected respectively to thermic influence of the current and voltage conditions of such circuit.

2. In a controller for electric circuits subjected to current and voltage variations, the combination with a switch, of operating means therefor comprising a member tending to effect operation thereof and releasable restraining means for said member comprising an electro-thermally responsive element subjected to thermic influence of one of said electrical conditions of such circuit and associated electro-thermic means for subjecting said element to thermic influence of the other of said electrical conditions of such circuit.

3. The combination with an internal combustion engine, a battery, a dynamo electric machine to be connected across said battery for cranking said engine and to be thereafter driven as a generator by said ongine to supply a load clrcuit, electro-responsive switches to control the connection of said machine to said battery and said load circuit respectively and control means for said switches providing for automatic starting of the engine. upon connection of a translating device to said load circuit, certain of said switches being subject to temporary deenergization upon short-circuiting of said load circuit, of means for curtailin telegraphing of said switches under suc conditions comprisin an electro-thermally responsive device adapted to control the energizing circuit of certain of said switches.

4. The combination with an internal combustion engine, a battery, a dynamo electric machine to be connected across said battery for cranking said engine and to be thereafter driven as a generator by said engine to supply a load circuit, an electro-responsive starting switch to connect said machine across said battery for starting, an electro responsive running switch and speed,responsive means and electro-responsive means for controlling the energizing circuit of said starting switch, of additional electro-thermally responsive control means for said circuit to be subjected to influence in accordance with both the current and the voltage condition of said cranking circuit.

In witness whereof, I have hereunto subscribed my name.

- GUY R. RADLEY. 

